Centralized traffic controlling system for railroads



MairchZ, 1937. E. o. BLQDGETT CENTRALIZElj TRAFFIC CONTROLLING SYSTEM FOR RAILROADS 5 Sheets- Sheet 1 Filed Oct. 13, 1933 53m Em.

* m w nmpuwcco I Hm L230 zmsok INVENTO f. 0. /& BY MM ATTORNEY 8 50 L ou March 2, 1937. E. o. BLODGETT CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Oct. 13, 1935 5 Sheets-Sheet 2 INVENT 0 BY M 4 ATTORNEY March 2, 1937. E. o. BLODGETT 2,072,079

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Oct. 13, 1935 5 Sheets-Sheet 3 ATTORNEY March 2, 1937. E. o. BLODGETT 2,072,079

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS 5 Sheets$heet 4 Filed 091;. 15, 1933 9N mmm INVENTC%%- 0M M ATTORNEY 'March 2, 1937. E. o. BLODGETT 2,072,079

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILOADS 5 Sheets-Sheet 5 Filed Oct. 15, 1933 INVENTO 6. d 7 BY Patented Mar. 2, 1937 STATS PATEN'i QFFICE CENTRALIZED TRAFFIC CONTROLLING SYS- TEM F012. RAILROADS Application October 13, 1933, Serial No. 693,484

9 Claims.

This invention relates to centralized trafiic controlling systems for railroads and it more particularly pertains to the communication part of such systems.

The present invention contemplates a centralized trafiic controlling system of the type in which the switches and signals at various points along a railroad system are placed under the control of an operator in a central control office, in such 10 a Way that the operator may at will change the positions of the switches, subject to automatic approach and detector locking circuits which prevent unsafe operation of any switch and in such a way that the operator may at will hold at stop any of the signals or allow them to clear dependent upon the position of the associated switches and also provided the location of trains makes it safe for such signals to indicate proceed.

In that type of centralized trafiic controlling :3 system where a communication system of the transmitted to the control oifice in accordance with the positions of the various traflic controlling devices at the several field stations and these indication impulses are transmitted to the control oiiice, one station for each operating cycle.

:7 Since the system of the present invention is of the coded duplex type, it is operable through es of operation for the transmission of cont1 v-3 and/ or for the transmission of indications. When controls are transmitted, a particular field :5 a station selecting code is first transmitted to select the desired station and this code is then followed by "e controls to be transmitted to the selected station. Similarly, when indications are transthat particular field station which is a. initting first transmits its station registerg code followed by the transmission of the inttions at that station. The system chosen as one embodiment of the pi t invention provides that the control oifice e field stations are connected in series by a stepping line circuit and a message line circuit comprising three line wires. These three line es are suppiied with energy from an alternatcurrent source, preferably located in the control ofiice, although such source might be located anywhere else along the communication system. .ernating current energy supplied to each uit is divided into two branches convenreferred to as the A branch and the B This division of circuits is accomplished out by the use of suitable one-way devices, such for example, as the common copper oxide rectifier so that the A branch may have current flowing in one direction only when it is closed and so, that the B branch may have current flowing in the opposite direction only when it is closed.

In the present embodiment, the A branch of the source of energy is connected to the stepping line circuit for governing the step-by-step operation required in a selector type system at the control office and at the several field stations. This A branch is also selectively connected to the message line circuit and serves to make up a portion of the code combination formed during the transmission of controls. The B branch is selectively connected to the stepping line and to the message line for completing the code combination used in transmitting controls. In the present invention this selective connection of the A and B branch circuits of the source of energy to the stepping and message lines for the transmission of controls is applied during the impulse periods which will be conveniently referred to as the on periods. The B branch is selectively connected to the stepping and message lines during the time spaces between impulse periods, which will be conveniently referred to as the oiT periods. The A branch is selectively connected to the message line during the off periods. This connection of the A and B branches to the stepping and message lines during the off periods is for the transmission of indications.

For example, when the A branch is connected to the stepping line circuit, an impulse is applied to this circuit for energizing the line relays in the control oflice and at all field stations in series. During the time that the stepping line is energized by Way of the A branch the stepping line may be energized or deenergized by way of the B branch as determined by the control code to be transmitted. Similarly, during the time that the stepping line circuit is energized by way of the A branch, the message line circuit may be selectively energized or deenergized by way of either or both the A and B branches, thus combining with this selective energization of the stepping line by way of the B branch to form the control code.

Likewise, since indications are transmitted during the ofi periods, the B branch is selectively connected to the stepping and message lines and the A branch is selectively connected to the message line during the off periods for energizing or not energizing these lines in combination for providing the indication code.

Although it is to be understood that the system of the present invention may be readily adapted for use in a. system of selective lock-out between field stations such as disclosed, for example, in the pending application of T. J. Judge, Ser. No. 613,353, filed May 25, 1932, the present embodiment has been shown as employing the so-called superiority of code principle. between the field stations. This arrangement provides that all field stations having new indications to transmit at the beginning of an operating cycle attempt to transmit their station registering code calls, but only that station having the most superior code call is successful in transmitting its complete code, while all of the other stations drop out for the remainder of that cycle and again endeavor to transmit their codes during the next cycle. In this way, the field stations are allowed to transmit their indications one station at a time in a sequence or order determined by the relative characteristics of the station registering code calls.

These characteristic features of the present invention thus briefly stated will be explained more in detail in the following description of one embodiment of the invention and various other features, functions and advantages of a system embodying this invention will be in part pointed out and in part apparent as the description thereof progresses.

In describing the invention in detail, reference will be made to the accompanying drawings in which those parts having similar features and functions are designated in the several views by like letter reference characters which are generally made distinctive either by reason of distinctive exponents representative of their location or by reason of preceding numerals representative of the order of their operation and in which:

Fig. 1 illustrates the line circuit arrangement for a control office and one field station in a system embodying the present invention, together with the apparatus most closely associated with these circuits.

Figs. 2 and 2A illustrate the apparatus and circuit arrangements employed at the control office for providing means whereby an operator may govern the switches and signals throughout the territory served by the communication system and for providing means whereby indications may be received from the various field stations throughout such territory.

Figs. 3 and 3A illustrate the apparatus and circuit arrangements employed at a typical field station for providing control of a single railway track switch and for transmitting indications to the control office, all in accordance with the present invention.

In considering the circuits illustrated in these figures in connection with the following description, Fig. 2 should be placed above Fig. 2A and Fig. 3 should be placed above Fig. 3A, with Fig. 3 to the right of Fig. 2 and with correspondingly numbered lines in alignment.

For the purpose of simplifying the illustrations and facilitating in the explanation, various parts and circuits constituting the embodiment of the invention have been shown diagrammatically and certain conventional illustrations have been employed. The drawings have been made more with the purpose of making it easy to understand the principles and mode of operation rather than with the idea of illustrating the specific construction and arrangement of parts that would be employed in practice. Thus, the various relays and their contacts are illustrated in a conventional manner and symbols are used to indicate the connections to the terminals of batteries or other sources of current instead of showing all of the wiring connections to these terminals.

The symbols and are employed to indicate the positive and negative terminals respectively of suitable batteries or other sources of electrical energy and the circuits with which these symbols are used always have current flowing in the same direction. It should be noted that the present embodiment employs direct current at the control oflice and at the field stations for energizing the local circuits while alternating current is employed for energizing the line circuits. However, it might be expedient to employ alternating current for the local circuits and in such event, the usual engineering expedients may be employed in adapting the operation of the system to an alternating source of energy. When alternating current is used in place of direct current, the particular symbols employed as representing local sources of energy should be considered as indicating the relative instantaneous polarities of the alternating current source substituted for the direct current source. The symbols (B+) and (B-) are employed to indicate the positive and negative terminals respectively of suitable batteries or other sources of current having mid-taps designated (UN). The circuits with which these symbols are used may have current flowing in one directic-n or the other depending upon whether ter:- minal (3+) or (B) is used in combination with the center tap (CN).

Communication system.-The general plan of organization of the system may be best understood by referring to Fig. l of the drawings which discloses the line circuits with the most closely associated apparatus. It is to be understood that the system may be extended to include as many field stations as necessary for the proper supervision of the territory allotted to a particular control ofiice but for convenience in disclosing the present invention only a first field station has been illustrated.

The line wires 3, iii and I2 connect the control office with the first field station and similarly, these line conductors extend from the first to the second field station and so on to the end of the system where they are connected together to provide closed circuits for conductors 8, l0 and it. Although the control onice has been shown located at one end of the system, it is to be understood that it may be located at any intermediate point or at the opposite end of the system since the present system is of the coded type employing a, superiority of code between field stations.

The line circuit is energized in the control office from a suitable source of alternating current indicated as being connected to the primary of transformer TR, with one terminal of the secondary of this transformer permanently connected to common conductor 12, while the other terminal is selectively connected to conductor l0 and message conductor 8. The alternating current may have the usual sine wave form and may have a frequency distinctive from the usual power lines in order to avoid interference.

The stepping line circuit including conductor Iii includes a line relay F at the control ofiice in series with a rectifier unit RA and a line relay F at the field station in series with a rectifier unit I RA These line relays are of the neutral type and it will be understood that similar relays and rectifiers are connected in the stepping line conductor at the other stations. Line Ml also includes a front contact 84 of a pulsing relay EP in the control office. Branch B of line ill at the field station includes a rectifier unit IRB in series with a message relay lME and certain contacts, the purpose of which will be described later in the specification. Branch B of line iii in the control office includes a message relay llvlE in series with a rectifier unit RB and contacts of certain relays, the purpose of which will be later explained.

Branch A and branch B in the control office are each connected through message relays ZME and Ell IE respectively to message line conductor 8 by the operation of certain relay contacts which will be thoroughly discussed. At the field station, the message line conductor is connected in series with message relay 2ME and rectifier unit 2RA The message line conductor is likewise connected to message relay 3ME in series with rectifier unit 2RB This connection of relays ZME and 8IvlE in series with message line conductor 8 is controlled by certain relay contacts as will be later explained.

It will be understood that the F and ME relays at the control ofiice and at the various field stations are controlled over the line circuits by half cycles of alternating current or in other words pulsating current. For greatest cfilciency, these relays may be designed with such characteristics that they will operate without undue chattering or vibration of the armature, although the con- Vcntional direct current telephone type relay will operate satisfactorily. An expedient employed to provide proper operation of these relays may include shunting the relay windings with suitable resistors, rectifier units or by a resistor and a condenser in series. Likewise, a special design of the magnetic circuits of these relays may be provided to hold over the relay armature between successive energizations of its windings on successive waves of the alternating current.

Control ofiice cqwipment.-The control office (see Figs. 2 and 2A) includes a control machine having a group of control levers for each of the field stations, a miniature tracl: layout corresponding in every way to the actual track layout in the field and various indicating lamps or equivalent devices, together with the apparatus and circuits to accomplish the functioning of the system.

That part of the control omce illustrated shows more particularly those devices of a control machine which are typical of the apparatus associated with a single field station having a track switch, a cross-over or the like, together with the general transmitting apparatus used in common by all such field stations.

The apparatus for one track switch includes a signal control lever SGL, a starting button SB, a minature track switch point ts and track switch "on indicating lamps N and R. Similarly a S'F/Ccoll. control lever or levers (not shown) would also be associated with the apparatus of he same field station, but these devices have been omitted for convenience in the description since the control of the signals by lever SGL may be considered as typical of the control of other trafilc controlling devices.

The movement of the signal lever to one eX trerne position or the other, or when this lever is left in its neutral position, followed by the actuation of the starting button results in clearing the corresponding signals at the field station asso ciated with the starting button, or putting the signals to stop in accordance with the position of the signal control lever, through the medium of one code determining relay for a particular station may be pick d up during any one particular cycle of operations. This interlocked bank or relays is so arranged that if several storing relays are up at the same time their corresponding code determining relays will be picked up successively during successive operating cycles in a predetermined order as determined by their location in the code determining relay bank, all of which has been completely disclosed in the prior application of N. l). Preston et al., Ser. No. 455,304 filed May 2Q, 1930, corresponding to Australian Patent 1,501 of 1931.

The control office includes a neutral line relay F and associated line repeating relays F? and which repeat each energization and deenergizaticn of relay F. The l e repeating relay 2?? is for the purpose of obtaining suitable time margins. Slow acting relay SA is picked. up at the beginning of each cycle and is dropped at the end or" each cycle. This relay has such slow acting characteristics that its pick-up time is relatively slow compared to the pick-up time of the neutral relays such as 5F? and 2F? for example, but the drop-away of relay SA is comparatively longer than its pick-up period.

Associated with the line relay and its repeating relays is a bank of relays including stepping relays iV, 51V, 3V and half step relay VP. This bank of relays marks off the s .ccessive steps of each cycle of operations. An impulsing relay E is jointly controlled by the stepping relays and the half step relay. This iinpulsing relay, together with its repeating relay EP, governs the opening and closing of the A branch of the circuit connection to the stepping line.

The B branch of the A. C. supply is electively connected to the stepping line each on period by reason of the decnergized or energised condition of the code sending relay lCS. The A branch of the A. C. supply is selectively con nected to the message during each on period by reason of the doc or energized condition of the code The B branch of the A. C. J is selectively con-' nected to the each on period by reason of the dcenc zed or energised condition of the relay These code sending relays are of the neutral ype and are energized or left deenergized on each step in accordance with the station code call the particular controls to be transmitted during a particular cycle of operations following the selection of a station.

Message receiving relays ill IE, 2MP] and 3MP] are eiiective during each oil period to position on the corresponding step suitable pilot relays in accordance with their conditions (energized or deenergized). This conditioning of the mes sage receiving relays is determined at the field station by the particular code transmitted.

For the purpose of illustrating the registration of a field station, only one station relay C has been shown, which relay is indicated as being selected in accordance with the character of the code impulses for the first two steps. In other words, any suitable pilot relay bank such as disclosed for example in the above mentioned prior application of N. D. Preston et al., Ser. No. 455,304 may be employed for registering the station code call and for selecting the particular station relay C associated with the calling station. The remaining steps of the cycle are thereafter effective to register the condition of the message receiving relays IME, ZME Ell/IE for positioning indication storing relays such as relays HR and 21R in accordance with the indications being transmitted from the registered field station.

A starting relay ST is provided for causing the system to initiate a cycle of operations whenever this relay is picked up with the system at rest. This relay may be energized by reason of the presence of any controls to be transmitted from the control office or by reason of the presence of any indications to be transmitted from one or more field stations.

The control office also includes various sources of current supply, bus wires and circuit connections, indicator lamps, terminal boards, overload protection and such other devices as may be required for the proper functioning of such a system.

Field station equipment-The field station illustrated in Figs. 3 and 3A is typical of all field stations of this system and may be adapted for use at the first, second or any other location by merely altering certain code jumpers and connections to arrange for the desired codes assigned to the various locations. For convenience in describing the present invention the apparatus illustrated in Figs. 3 and SA has been designated as associated with the first field station by reason of the distinctive exponent (1) employed with each of the letter reference characters.

With reference to Fig. 3, a turn-out track is illustrated as connected to a main track by means of a track switch TS which may be operated from one extreme locked position to the other by a suitable switch machine SM. This switch machine is governed by a switch control relay (not shown) which is controlled from the control ffice through the medium of the communication system herein disclosed.

Suitable signals (not shown) are associated with the track switch TS for governing traffic thereover and are provided with automatic signaling means interrelating the trafiic over this switch with such other track switches and track sections as be associated therewith. These signals are contemplated as being governed from the control ofiice through the medium of the communication system by control relays such as direction relay DR and stop relay S of Fig. 3A.

Certain other devices such as the usual track relay, the track battery, as well as the usual lock relays have been omitted from the present disclosure for the sake of simplifying the drawings and description.

The communication part of the system ineludes at the field station a line relay F and its associated repeating relays EFP and 2FP all or the neutral type. These relays, like the corresponding relays in the control orifice, follow each energiaation and each deenergization of the stepping line from the A branch of the source of current supply. Slow acting relay SA corresponds to relay SA in the control ofiice and has similar characteristics and functions.

The field station includes a bank of stepping relays including relays IV 2V 3V together with a half step relay VP arranged and controlled in a similar manner as the stepping re-. lay bank in the control office, with certain exceptions which will be later explained in detail.

The field station includes a selecting relay S0 which is responsive to the station selecting code calls transmitted from the control ofiice, so as to select the corresponding field station and render this station effective to receive succeeding control impulses whenever the code call corresponds to the one assigned to this field station. Similarly, a selecting relay S1 is provided to be responsive to the code calls transmitted from the field stations, so that when the resulting code call corresponds to that assigned to its station this station will be effective to permit transmission of indications to the control oflice.

A change storing relay CI-IS is provided to register a change in any of the trafiic controlling devices at the field station such as the track relay (not shown) the switch repeating relay W1 etc, so that the system will be initiated for the transmission of new indications when this change storing relay is picked up. The specific control for this relay has not been illustrated since it may be any approved arrangement such as disclosed in detail in the patent to D. F. DeLong et al. Pat. No. 1,852,402 issued April 5, 1932. The change storing relay when once energized can be deenergized only when its field station has been effective in registering its code call in the control office.

For the purpose of applying the code call of the field station by way of the B branch of the A. C. supply to the stepping line in accordance with the positions of station code jumpers Edi, a code sending relay lCS of the neutral type is provided. For the purpose of applying the code call of the field station by way of the A branch of the A. C. supply to the message line conductor in accordance with the positions of the station code jumpers Edit, 2 3i a code sending rela 205 of the neutral type is provided. For purpose of applying the code call of the field station by way of the B branch of the A. C. supply to the message line conductor in accordance with the positions of the station code jumpers 2%, Ziil, a code sending relay 308 of the neutral type is provided.

These code sending relays are subject to the control of the selecting relay S1 so that they are rendered ineffective during a cycle of operations in which this field station is endeavoring to transinit, as soon as this station fails to be selected by reason of th differences between the code call actually transmitted to the control office and the code call assigned to this field station. This control of the CS relays by the SP relay is efiected by shunting the CS relay contacts by back contacts on the S1 relay, closed when this latter relay is dropped.

Relays iME Ell IE and tME are effective in similar branches of the circuits and over similar line conductors as corresponding relays in the.

control office for selectively energizing the selecting relay S0 and the selecting relay S1 as well as controlling the conditioning of the controlled relays at the selected station in accordance with the code combinations received over the communication system, all in a manner which will be explained in detail.

Two rectifiers lRA and IRE (or a single rectifier device with a center tap) are connected in the stepping line circuit at each field station for selecting the A and B branches of the A. C. supply which is connected to the stepping line. Two rectifiers 2P.A and ZRB (or a single rectifier with a center tap) are connected in the message line conductor for providing two separate circuit paths for the A and B branches of the A. C. supply in connection with the message line conductor at each field station.

For illustrating the manner in which indications are transmitted from a registered field station in groups of three for each step of the stepping relay bank, a switch repeating relay WP is provided. The three conditions repeated by this relay are, first the corresponding switch unlocked, second the corresponding switch locked in its normal position and third the corresponding switch locked in its reverse position. The first condition is indicated by the neutral contact Z'lii of relay WP being dropped and the second and third conditions are indicated by the neutral contact us up and polar contact 21 9 of relay WP in its left and right hand positions respectively. For illustrating the manner in which controls are transmitted to a selected station in groups of three for each step, a stop relay S and a direction relay DR are provided. The three conditions received and recorded by these relays are, first putting all signals to stop, second clearing signals east and third clearing signals west.

The field station also includes suitable bus wires, circuit connections, code jumpers and such other devices as are necessary for a centralized trafilc controlling system as contemplated in accordance with the present invention.

It is believed that the nature of the invention, its advantages and characteristic features, can be best understood with further description being set forth from the standpoint of operation.

Operation The communication system of the present invention is normally in a condition of rest from which it may be initiated into a cycle of operations either from the control office or from any of the field stations when there are new controls or new indications ready to be transmitted. If new controls are ready for transmission to several different field stations at substantially the same time, they are transmitted on separate cycles of operation, one station for each cycle. Similarly, if several field stations have indications ready for transmission at substantially the same time, they are transmitted from such field stations, one station at a time on separate operating cycles.

Whenever there are new controls and new indications ready for transmission at the same'time, controls re transmitted to a particular field station on the same operating cycle that indications are transmitted from the same station or from some other selected station, depending upon the particular station having new indications to transmit.

Irrespective of whether a cycle or" operations is for the transmission of controls and/or indicaticns, a predetermined number of time spaced impulses are applied to the stepping line circuit by way of the A branch of the source of current to accomplish the step-by-step operation of the stepping relay banks at the control office and at each field station. Each series of impulses includes a relatively long conditioning impulse at the beginning of the cycle, while the remaining impulses of the series are of substantially equal duration. Also, the time spaces between the impulses of each series are of substantially equal duration.

The stepping relay bank in the control office is arranged to take one step for each of the time spaces of any series of impulses applied to the steppin lino circuit. The stepping relay banks at the field stations are arranged to take one step for each of the impulse periods of such series of impulses. Thus, the stepping relays in the ethos are picked up during the off periods and the stepping relays at the stations are picked up during the on periods. The half step relay VP in the control ofiice is shifted during the on periods, that is, it is picked up and dropped during alternate on periods. The half step relay VP at the field station is shifted during the off periods, that is, it is picked up and dropped during alternate or? periods. This also refers of course, to the stepping relays and the half step relays at other stations since they operate in synchronism with those at the typical station illustrated in the drawings.

Whenever a cycle of operations is initiated for the transmission of controls, the characters of the impulses placed upon the stepping line circuit by Way of the B branch of the A. C. supply and the characters of the impulses placed upon the message line circuit by way of both the A and B branches of the A. C. supply during the on periods are determined in accordance with the station to be selected and the controls to be transmitted to the selected station, as set up by the code jumpers and control levers associated with the corresponding station in the control ofiice.

On the other hand, during a cycle initiated for the transmission of indications, the characters of the impulses placed upon the message line circuit by way of the A and B branches of the A. C. supply and the characters of the impulses placed upon the stepping line circuit by way of the B branch of the A. C. supply during the off periods are determined in accordance with the positions of the code jumpers at the station to be registered in the control ofiice and the indication contacts on the various indication devices at that station.

If controls are being transmitted alone, then a non-registering or phantom code is applied to the stepping and message line circuits during the indication transmitting periods. If indications are being transmitted alone, then a non-selecting or phantom code is applied to the stepping and message line circuits during the control transmitting periods. When both controls and indications are being transmitted, the characters of the impulses during the respective transmitting periods are determined in accordance with their respective code transmitting means.

Normal conditiom..Although the system is illustrated as being in a condition of rest, the message line circuit is normally energized by way of the B branch in order to permit any field station to initiate the system into a cycle of operations. This energizing circuit extends from the upper terminal of transformer TR of Fig. 2, common line conductor l2'through all of the field stations in series, returning by Way of message line conductor 29!! through all of the field stations in series, back contact 233 of relay S1 winding of relay ZME rectifier 2RA message line conductor 8, back contact ll of relay F, winding of relay ZME and rectifier BA to the other side of the transformer. It will be assumed that only the positive half cycles of the A. C. current from transformer TR flow through the above described circuit and this circuit is effective to energize relay 2ME.

A branch circuit may be traced from message line conductor 8 in Fig. 2 which extends through back contact l3 of relay F, winding of relay 3MB and through rectifier RB to the lower side of transformer TR. The opposite half cycles of the A. C. current (for example fiow through this circuit and this current is efiective to energize relay SME. An additional branch from the return line conductor at the end field station extends by way of stepping line conductor 29E through all of the field stations in series, back contact 264 of relay S1 winding of relay lME back contact 205 of relay ST rectifier lRB stepping line conductor to, back contact I5 of relay F, winding of relay IME and rectifier RB to the lower terminal of the transformer TR. Current during the negative half cycles flowing over this circuit is effective to energize relay lME.

Since the above described circuits including relays IME, 2MB and SME also include corresponding relays lME 2ME and 3ME at the field station, these latter relays are likewise normally energized. The remaining circuits of the system are normally deenergized with but a few exceptions. For example, track switch repeating relay WP associated with track switch TS is preferably of the closed circuit type. Also, the detector track circuit including the usual track relay, as well as the usual signals-at-stop relay and the change relay are normally energized but in order to eliminate undue complications, these circuits have not been shown in detail. Relay ZCS is normally energized over a circuit extending from back contacts 24!, 242 and 2&3 of relays 3V 2V and IV respectively, jumper 200, bus 239 and winding of relay 2CS to Manual starting.-With the system in a condition of rest, it may be manually initiated into a cycle of operations for the transmission of controls. To initiate such a cycle, the operator first positions the control levers for the field station or stations to which controls are to be transmitted and he then actuates the starting button or buttons associated with this station or stations.

For the purpose of considering the operation of the present invention, it is sufficient to know that the actuation of starting button SE of Fig. 2, for example, causes the actuation of code determining relay CD in its proper turn while the system is at rest. The response of relay CD, or any other code determining relay (not shown), closes a pick-up circuit for starting relay ST extending from back contact if of relay SA, front contact ll of relay CD and winding of relay ST, to It will be understood that the bus Wires to which front contact I1 is connected extend to the remaining code determining relays in the bank.

The response of relay ST closes a pick-up circuit for relay E extending from front contact [8 of relay ST, back contact IQ of relay VP,

lower winding of relay E, back contact 25 of relay IV, back contact 2| of relay 2V and back contact 22 of relay 3V, to The energization of relay E is repeated by relay EP upon the closure of front contact 23 of relay E.

The closure of front contact i i of relay EP energizes the stepping line conductor to over the A branch of the A. C. portion of the circuit. This energizing circuit for the stepping line conductor extends from the lower terminal of transformer TR through rectifier RA, relay F, front contact M of relay EP, stepping line conductor ill, rectifier lRA relay F conductor 29! extending through the A branches including the line relays at other field stations and thence through the tie at the end field station and by way of common return conductor E2 to the upper terminal of transformer TR. This energization of the stepping line conductor is repeated at the control office and at each field station by the response of the line relays.

The response of the line relays is repeated by their respective repeating relays WP and 2FP in the control office and relays IFP and ZFP at the illustrated field station. For example, relay lFP is energized upon the closure of front contact 24 of relay F and relay ZFP is energized upon the closure of front contact 25 of relay lFP. Relay [FF is energized upon the closure of front contact 206 of relay F and relay 2FP is energized upon the closure of front contact 26? of relay lFP The picking up of the F and FF relays in the control office and at each field station is repeated by their respective slow acting relays. For example, the picking up of front contact 26 of relay F and front contact 2'! of relay lFP in the control oifice closes an obvious energizing circuit for relay SA. The picking up of front contact 208 of relay F and front contact 289 of relay lFP closes an obvious energizing circuit for relay SA at the field station.

The response of relay SA in the control office closes a pick-up circuit for relay VP extending from front contact 28 of relay SA, front contact 29 of relay F, back contacts 3t, 3t and 32 of relays 3V, 2V and IV respectively and the upper winding of relay VP, to The picking up of front contact 33 of relay VP closes a stick circuit for this relay which is independent of contacts 30, 3| and 32 of the stepping relays. The response of relay SA at the field station is not followed by the response of relay VP until the following deenergized period of the stepping line circuit.

Although the station selecting relays S0 and SI at the field station are initially conditioned for selection during the pick-up periods of their respective slow acting relays together with the conditioning of various other devices, such operations will be considered separately. Attention is more particularly directed at this time to the manner in which the stepping line circuit is impulsed with time spaced impulses over the A branch of the source of supply for marking off the ofi and on periods of the cycle.

Impulsz'ng operation.As above mentioned, the first energized period of the stepping line circuit is provided by the actuation of relay EP as a result of starting relay ST being picked up. Like-,

wise, the successive energizations of relays F. IFP and ZFP are effected. Assuming for the moment that relay VP responds as above pointed out, the opening of its back contact is deenergizes relay E. The dropping of front contact 23 of relay E deenergizes relay E? which in tum deenergizes the stepping line by opening front contact it.

It will be pointed out at this time that the pickup of back contact 66 of relay SA deenergizes relay ST but the dropping of front contact is of relay ST is not effective to remove the control of relay E from the VP and stepping relays. This is because the closure of front contact 23 of relay SA places potential upon the control circuits of relay E and maintains this potential throughout the cycle of operations.

The deenergization of relay F during the first off period is repeated by relays WP and ZFP in succession. Since relay SA is sufficiently slow acting, its contacts are maintained in their picked up positions between successive on periods of a cycle although the energizing circuit of relay SA is opened during the off periods. The re sponse of relay F to the first off period causes relay iv to be picked up over a circuit which will be later pointed out.

The response of relay l V with relay VP picked up closes an energizing circuit for relay E which ektends from front contact 28 of relay SA, front contact ill of relay VP, upper winding of relay E, front contact 2d of relay iv and back contacts 2i and 22 of relays 2V and 3V respectively, to The picking up of relay E is repeated by relay EP which again energizes the stepping line circuit over the A branch of the source of supply for marking the beginning of the second on period.

The second energization of the stepping line circuit is repeated by relays F, IFP and ZFP as before. The response of relay P causes relay VP to be deenergized as will be later explained. The dropping of front contact [9 of relay VP opens the energizing circuit of relay E which drops, followed by the dropping of relay EP which in turn deenergizes the stepping line circuit to mark the end of the second on period and the beginning of the third off period.

the embodiment of the present invention, this impulsing of the stepping line circuit con-- tinues in the above described manner for four on periods separated by off periods to comprise a cycle of operations, It will be apparent that the impulses are time spaced as determined by the response of the stepping relay bank in the control office. Briefly, each on period causes the actuation of the contacts of relay VP to opposite positions while each off period causes the picking up of the next succeeding stepping relay. The response of relay VP causes the dropping of relays E and EP for deenergizing the stepping line, while the response of the stepping relays during each off period causes relays E and EP to be picked up for energizing the stepping line with the next impulse. The stopping of the impulsing at the end of a cycle by prolonging the off period will be explained in detail when considering the operations effected at the end of the cycle.

Having pointed out in detail how a series of time spaced impulses are applied to the stepping line circuit through the A branch of the source of supply, the response of the stepping relay banks at the control oflice and at the field stations may now be considered.

step by-step operations-The stepping operations will be considered with particular reference to the stepping relay bank illustrated in the control office (see Fig. 2), while those exceptions with regard to the operation of the corresponding stepping relay banks at the field stations will be pointed out more particularly with reference to the typical field station (see Fig. 3)

The application of the first impulse to the stepping line circuit by way of the A branch of the source of current supply as repeated by line relay F causes relay VP to be picked up over a circult which has been previously described. The stick circuit closed by front contact 33 of relay VP has likewise been described.

With the contacts of relay VP picked up, the pick-up circuit for stepping relay lV is prepared so that when the first off period is repeated by the dropping of relay F, a pick-up circuit for lay 5V is completed which extends from back contact 25 of relay F, front contact 1 24 of relay SA, front contact of relay VP, back contact 3d of relay 2V and winding of relay iv, to Relay EV closes a stick circuit for itself extending from front contact 28 of relay SA, front contact ill and winding of relay 9V, to

The response of relay IV prepares the circuit for the differential winding of relay VP so that when the second on period is repeated by the picking up of relay relay VP is deenergized and its contacts are dropped. This diiferential energizing circuit for relay VP extends from front contact 28 of relay SA, front contact 29 of relay F, back contacts 38 and 35 of relays 3V and 2V respectively, front contact 32 of relay 5 V, front contact 38 and lower winding of relay VP, to Since the two windings of relay VP are energized in opposite directions, the magnetic fiux in the core of relay VP is reduced substantially to zero causing it to release its armature. The dropping of front contacts 33 and 38 deenergize both windings of this relay, therefore it remains in its deenergized position until its pick-up circuit is again closed.

With relay VP deenergized, the pick-up circiut for relay 2V is prepared so that when the next off period (second) is repeated by the dropping of relay F, stepping relay 2V is picked up over a circuit which extends from (-1-), back 26 of relay F, front contact 34 of relay SA, back contact of relay VP, back contact of relay 3V, front contact ii of relay iV and winding of relay 2V, to Relay 2V closes a stick circuit for itself extending from front contact 28 of relay SA, front contact l! and winding of relay 2V, to

This step-by-step operation continues throughout the cycle until the last step has been taken. It will be apparent that for each on period of the stepping line circuit by way of the A branch of the source of supply relay VP is actuated to a new position, while during each off period of this same circuit the next stepping relay is picked up. Those stepping relays which pick up at each step are stuck up until the end of the cycle under the control of relay SA.

The step-by-step operations of the stepping relay banks at the several field stations are identical, so that an explanation of this operation in connection with Fig. 3 may be considered as typical of all field stations. At each station, the operation of the stepping relay is made dependent upon station selection as rendered effective by the selecting relays S0 and SP, for example. For the purpose of considering the stepping operation before the station selection function has been described, it may be assumed that at least one of the selecting relays S0 or S1 picked up so that at least one of the front contacts 2M3 or 25 i will be closed.

The response of relay SA at the beginning of the cycle does not close a pick-up circuit for the VP relay or for any stepping relay. During the first oif period relay F is dropped for closing a pick-up circuit for relay VP which extends from front contact 2l2 of relay SA back contact 21 3 of relay F back contacts 2H2, 255 and 255 of relays 3V 2V and W respectively and upper winding of relay VP to Relay VP closes a stick circuit for itself extending from front contact 232 of relay SA front contact 2i? and upper winding of relay VP to During the next on period (second) as repeated by the picking up of relay F a circuit is closed for picking up relay iV which extends from front contact 2H3 or front contact 2 of one or the other of the station selecting relays, front contact 2i 8 of relay SA front contact Zlii of relay F front contact 223 of relay V1 back contact 22i of relay 2V and winding of relay 1V to Relay IV closes a stick circuit for itself extending from front contact 222 of relay 3A front contact 223 and winding of relay 1V to The stepping bank takes one step for each on period and relay VP is actuated. to opposite positions for each off period throughout the cycle as long as the pick-up circuits for the stepping relays are closed by one of the station selecting relay contacts 210 or 2i i.

It is considered unnecessary to point out the detailed operation of the stepping and half step relays since they are substantially identical with similar circuits already explained in connection with the control omce, with the obvious exception that these relays at the stations operate during opposite periods from corresponding relays in the control office.

Station selection for controls-The application of impulses to the stepping line circuit has been explained in detail. In brief, a series of impulses is applied to the stepping line from the source of current through the A branch and each of these impulses includes a series of half cycles of alternating current. This current flows in a direction permitted by the rectifying units RA and iRA at the control ofiice and at the field station. For convenience, the half cycles of A. C. current which fiow through the RA rectifiers will be referred to as impulses. This application of a series of impulses to the stepping line circuit causes the step-by-step operations.

The half cycles of A. C. current which flow through the RB rectifiers will be referred to as impulses. Therefore, the stepping line circuit be conditioned during the on periods by the impulses for the purpose of the transmission of control codes. Likewise, the message line circuit may be conditioned during the on periods by impulses and impulses for transmitting additional control codes.

The energy selectively applied to the stepping and message line circuits includes a series of and impulses by reason of the opposite arrangement of the RA and EB rectifying units at the control office and at the illustrated field station.v It will of course be understood that the additional field stations are supplied with rectifier units connected in the line circuits in the same manner as illustrated in Fig. 3, but it is believed unnecessary to complicate the drawings and description by showing these additional stations.

The energized and deenergized conditions of the stepping line circuit by impulses during on periods are employed for the transmission of controls as above mentioned while the off periods of the stepping line circuit are conditioned by impulses for the transmission of indications. The conditioning of the stepping and the message lines for the transmission of indications will be explained later; It is considered sufficient to know that so far as the field stations are concerned during a cycle of operations for the transmission of controls alone, the stepping and message line circuits are continuously closed as will be explained more in detail hereinafter.

As soon as the operator has actuated starting button SB which results in the response of relay CD, the code sending relays 20S and 3CS are conditioned in accordance with the first code jumper 42 associated with relay CD. When the first impulse is applied to the stepping line circuit causing relay F to open its back contact I5, the stepping line circuit is conditioned by applying or not applying impulses to the stepping line circuit as determined by front contact ll of relay iCS. More specifically, in the arrangement illustrated in Fig. 2 with jumper E2 disconnected from bus 43 relay ICS does not close its front contact 4'! and the stepping line circuit is not energized with impulses.

In the event that jumper s2 is connected in its right hand dotted position to bus 43, then a circuit is effective to pick up relay lCS which extends from back contact 48 of relay 3V, back contact 2 9 of relay 2V, back contact til of relay iV, front contact 5| of relay CD, jumper 42, bus 33 and winding of relay lCS, to The picking up of front contact 4'! of relay lCS allows the half cycles of current to flow over the stepping line circuit. This current flows over a circuit extending from the upper terminal of transformer TR, conductor l2, conductor 291, back contact 204, of relay S1 winding of relay IME back contact 205 of relay ST rectifier lRB conductor ill, front contact M of relay ICS, winding of relay IME and rectifier RB, to the lower terminal of transformer TR. Current flowing over this circuit is eifective to pick up relay IME at the field station and relay llViE in the control ofiice.

In the alternate condition, that is, jumper 42 not connected to bus 43, relay ICS is not picked up to close its front contact il so that the above described circuit through relays IME and IIME is not completed, with the result that these two relays are not picked up during the first on period after relay F drops.

It should be noted at this point that when relay F is energized, the control of the coding impulses applied to the stepping and the message line circuits during the on periods is with relays iCS, 20S and $08. For example, with relay F energized, back contact it removes the shunt from front contact l? of relay iCS, back contact H removes the shunt from front contact 53 of relay 2C5; and back contact it removes the shunt from front contact 54 of relay 3C3. Therefore, the impulses are applied or not applied to the stepping line circuit as determined by whether relay lCS is picked up or not. The impulses are applied or not applied to the message line circuit as determined by whether or not relay 208 is picked up. The impulses are applied or not applied to the message line circuit as determined by whether or not relay 30S is picked up.

(3n the other hand, with relay F deenergized, contacts I5, II and I3 shunt front contacts 41, 53 and 54 of relays ICS, 208 and 30S respectively so that the stepping and message line circuits may be energized with impulses and the message line circuit may be energized with impulses during the oifperiods as determined by the indication code transmitted.

The condition of relay ICS as selected by front contact I of relay CD is maintained until relay IV is picked up during the first ofi period. Shortly after the picking up of relay IV, relay F is picked up (during the second on period) and impulses are applied or not applied to the stepping line circuit by relay I CS being picked up or not picked up as determined by the connection of jumper 44 which is selected through front contact 50 of relay IV and front contact 52 of relay CD.

Relay 2V is picked up during the second off period and relay ICS is conditioned to impulse or not impulse the stepping line circuit with impulses when relay F picks up its back contact I5 at the beginning of the third on period, as determined by the connection of signal lever contact 55. This contact is selected by way of front contact 59 of relay 2V and front contact 56 of relay CD. If contact 55 is in its neutral position, relay ICS will be picked up to apply impulses to the stepping line during the third on period, after the picking up of contact I5 of relay F, but if contact 55 is not in its neutral position, relay ICS Will be down so that impulses are not applied to the stepping line after relay F picks up its back contact I5 in the third on period.

Similarly, for each of the remaining steps the control of relay ICS is shifted from one contact of relay CD to the other so that relay ICS is picked up or not as determined by control lever contacts or jumper connections, all in accordance with the arrangement of these contacts and connections in the system.

Relay ZCS is connected to bus 45 and this bus is energized or not energized as determined by the jumper and controllever contact connections during separate steps of the operating cycle. Likewise, relay 30S is connected to bus 46 which is selectively conditioned in a like manner as determined by the jumper and lever contact connections at difierent steps of the cycle.

If relay 2CS is picked up during an off period by the energization of bus 45 when the stepping relay picks up during this off period, then the message line circuit is impulsed during the succeeding on period with impulses over a circuit extending from the lower terminal of transformer TR, rectifier RA, winding of relay ZME, front contact 53 of relay 20S, conductor 8, rectifier 2RA winding of relay 2ME back contact 203 of relay S1 conductor 29!] and conductor I2 to the upper terminal of transformer TR. If relay 20S is not picked up during a particular off period, then when relay F picks up its back contact II during the succeeding on period, the message line circuit is not impulsed with impulses.

If relay 30S is picked up during a particular off period, the message line circuit is impulsed with impulses during the succeeding on period over a circuit extending from the upper terminal of transformer TR, conductor I2, conductor 290, back contact 226 of relaySP, winding of relay 3ME rectifier 2RB conductor 8, frontcontact 54.0f. relay 30S, :winding of relay the on periods for obtaining a choice of eight different combinations per step. It will be recalled that the stepping line circuit is impulsed with impulses for controlling the stepping in the ofiice and at the stations. Therefore, impulses applied to the stepping line cannot be used for control code combinations. The eight different control code combinations obtainable during each on period are as listed in the following typical code table:

First typical code table-Fo r first step Stepping Message Message Code Line B Line A Line B Branch Branch Branch In the above table 0 represents an open jumper which is effective to deenergize the associated line circuit. and -1- each represent a closed jumper which is effective to energize the associated line circuit with and impulses respectively. The first combination energizes the IME relays. The second combination energizes the ZME relays. The third combination energizes the 3MB relays. The fourth combination energizes the IME and ZME relays. The fifth combination energizes the IME and 3ME relays. The sixth combination energizes the ZME and SME relays. The seventh combination energizes the IME, 2ME and 3ME relays. The eighth combination does not energize any of the ME relays.

The code jumpers and the signal control lever connected in the combination shown in Fig. 2 of the present embodiment are effective to condition the stepping and message line circuits during the three on periods in accordance with the following typical code table.

Second typical code table First Second Third Lme step step step Stepping B branch 0 Message A branch.-. 0 0 Message B branch 0 0 0 of the cycle.

apparent that more'than one ME relay can be simultaneously energized, for example, relays IME, 2ME and 3ME (and the corresponding relays at the stations) to provide the seventh choice by connecting three jumpers such as jumper 42 to all three buses 43, and 4B for a particular step.

It is thus seen how the stepping and message line circuits are conditioned in accordance with the positions of the three code sending relays during the on periods of the cycle. The eight combinations listed in the first typical code table above, which are obtainable on each step of the stepping relay bank, may be expanded so that the total number of combinations equals eight raised to the power of the number of steps. For example, sixty-four different combinations may be obtained with two steps. This will be evident by noting that any of the eight combinations listed in the above first typical code table can be used on the second step in connection with each one of the eight combinations obtainable on the first step.

These conditions of the two line circuits are rendered effective at the several field stations so as to select a particular station in accordance with the code transmitted and to actuate suitable control code storing relays in accordance with the controls transmitted. Before considering how these conditions of the two line circuits are effective to select a field station, such as the typical field station illustrated in Fig. 3, in accordance with the positions of the code jumpers in the control office illustrated in Fig. 2, it is necessary to know that the station selecting relays are picked up at all of the stations during the first on period of the stepping line circuit at the beginning For example, relay S0 at the first field station is picked up, as soon as relay F is picked up, over a circuit extending from front contact 22'! of relay F back contact 228 of relay SA and lower winding of relay S0 to Similar circuits are effective to pick up the SO relays at all other stations.

With all of the SO relays picked up, all of the field stations are then in readiness to be selected or dropped out. The system of the present invention employs the familiar Baudot code wherein the number of selections with a given number of code impulses, when a choice of eight characters may be had for each impulse, is equal toeight raised to the power of the number of impulses. It may be well to note that one eighth of the stations are selected on the first codeimpulse and the other seven eighths are dropped out. One eighth of those selected on the first impulse are selected on the second impulse and the other seven eighths are dropped out. This process of elimination continues until only one field station remains. The code jumpers in the control ofiice cause the code sending relays lCS, 2G8 and 30S to transmit the code combinations above noted, to which all SO relays are subjected at the beginning of the code but at the end of the code only one SO relay remains picked up.

It will now be explained how the station illustrated in Figs. 3 and 3A is selected in accordance with the arrangement of code jumpers 42 and 44 selected by relay CD of Fig. 2. Recalling that relay S0 was picked up at the beginning of the first on period, it will be noted that both the pick-up and holding circuits of relay S0 are open after relay SA is picked up. The pick-up circuit is open at back contact 228 of relay SA and the holding circuit is open at back contact 229 of relay 2FP and at back contact 230 of relay F Therefore, relay S0 is dependent upon its selecting stick circuit for energization.

At the time the stepping line is energized with current for providing the first on period, the stepping and message line circuits are coded as indicated in the first step column of the above second typical code table. The stepping line is not energized with impulses over the B branch as indicated by the 0 symbol associated with this branch at the first step. Therefore, relay lME of ,Fig. 3 is dropped. The message line is impulsed with impulses over the A branch during the first on period as indicated by the symbol which is effective to maintain relay ZME. picked up. The message line is not impulsed with impulses over the B branch as indicated by the 0 symbol which is elfective to drop relay 3ME In this discussion it will be understood that relays similar to IME ZME and 3ME located at all other field stations are conditioned in the same manner as those at the illustrated field station.

It will be pointed out at this time that the field station code jumpers such as 200 and 20! connect to the buses which lead to relays I CS 2CS and 308 in the same order that the code jumpers such as 42 and 44 of Fig. 2 connect to the buses Which lead to relays ICS, 208 and 30S. Inother words, the combination of code jumpers associated with a particular energized CD relay will cause the selection of a field station having its code jumpers connected in the same combination.

With relay IME down, relay ZME up and relay SME down during the first on period as above described, relay S0 is maintained energized by reason of a selecting stick circuit extending from' back contact 23! of relay ICS back contact 232 of relay IME front contact 233 of relay 208 front contact 234 of relay 2ME back contact 235 of relay 305 back contact 236 of relay 3ME front contact 231 and upper winding of relay S0 to It will be noted that relay ICS is not picked up because there is no jumper connection for energizing bus 238 during the first on period. Relay 2CS is picked up over a circuit extending from back contact 24! of relay 3V back contact 242 of relay 2V back contact 243 of relay [V jumper 200, bus 239 and winding of relay 2CS to Since bus 240 is not energized, relay 308 is not picked up.

It will be obvious that at all other field stations where the code jumpers corresponding to jumper 20B are connected to buses similar to 239, the selecting stick circuits for the SO relays Will be completed. On the other hand, at all other field stations where the code jumpers corresponding to jumper 200 are connected either to the buses corresponding to 238 or 240, the selecting stick circuits for the SO relays at those stations will be opened.

The first off period is repeated by the dropping of relays F WP and 2FP at the first field station. Similar relays at all other field stations of course are likewise dropped. This .completes a holding stick circuit for relay S0 extending from front contact 264 of relay SA back contact 230 of relay F in multiple with back contact 229 of relay 2FP front contact 244 and lower winding of relay S0 to Therefore, at the beginning of an off period, back contact 230 of relay F initially closes the holding stick circuit of relay S0 before relay IV in the control oifice shifts the control of the CS relays to the second code. During the .on period, the back contact 229 of relay 2FP finally opens the holding stick circuit of relay S0 but this does not occur until the code selecting relays ICS 20S and 3C8 and the message receiving relays IME 2ME and 3ME at the field station have been conditioned in accordance with the code applied to the line during this on period.

The application of the second impulse to the stepping line for providing the second on period is repeated by the picking up of relays F lFP and 2FP The code for the second step as indicated in the typical code table results in energizing the stepping line with impulses, in not energizing the message line with impulses and in not energizing the message line with impulses. This results in relay |ME at the field station being up and relays2lvlli. and 3ME being down. Relay ICS is picked up over a circuit extending from back contact 24! of relay 3V back contact 242 of relay 2V front contact 243 of relay IV jumper 20I, bus 238 and winding of relay 108 to Neither relay 2CS nor relay 3CS is energized during the second on period because buses 239 and 240 are deenergized.

The selecting stick circuit for relay S0 is now completed from front contact 23l of relay ICS front contact 232 of relay IME back contact 233 of relay 208 back contact 234 of relay 2ME back contact 235 of relay SCS back contact 236 of relay 3ME front contact 231 and upper winding of relay S0 to At all of those stations having code jumpers similar to 2D I connected to buses similar to 236, the S0 relays are maintained energized over their selecting stick circuits which are similar to that described in connection with the illustrated station. At those stations having code jumpers similar to 20! connected to buses similar to 239 and 2 36, the selecting stick circuits of the SO relays are not completed because there will be a lack of correspondence between one or more of the pairs of relays similar to 2CS 2ME 305 and 3ME The end of the second on period and the beginning of the second off period is marked off by the dropping of relays F IFP and ET". The holding stick circuit above described in connection with relay S0 is again completed at the illustrated station. In the present embodiment, station selection is illustrated as being accomplished during two steps of the cycle so that at this time only relay S0 of Fig. 3 will be in its energized position.

The end of the second off period and the beginning of the third on period is marked off by the picking up of relays F IFP and HT. Before relay ZFP picks up its back contact 229 to open the holding stick circuit of relay S0 a permanent stick circuit is established for relay S0 Relay 2V is picked up during the third on period before relay 2FP is picked up so that the permanent stick circuit is established from front contact 245 of relay 2V front contact 244 and lower winding of relay S0 to This permanent stick circuit is of course effective until the end of the cycle when the stepping relays are dropped at which time relay 2V drops its front contact 245.

Transmission of controZs.--From the above description, it will be seen how a station maybe selected when the code call of that station-agrees I with the code call transmitted over the stepping and message line circuits during the on periods. Assuming that the field station illustrated-in Fig. 3 has been selected by itsrelay S0 remaining' in an energized position until relay 2V is picked up, the application of the third impulse is repeated by relays F [FF and WP. The code impulses applied during the third on period are in accordance with the position of lever SGL in the control oflice, for example, and with this lever in the position illustrated in Fig. 2, this code combination is as follows: Stepping line energized with impulses, message line not energized with impulses and message line not energized with impulses. This is due to relays ZCS and 3CS not being picked up on this step because contact 55 is in its neutral position. Relay ICS is picked up over a circuit extending from back contact 48 of relay 3V, front contact 49 of relay 2V, front contact 56 of relay CD, contact 55 of the signal control lever in its neutral position, bus 43 and winding of relay l CS, to

This code combination results in relay IME being energized, relay ZME being deenergized and relay 3ME being deenergized. At this step the code' selecting relays at the field station have no function because the station has been selected prior to this step.

At the time relay 2V is picked up during the third on period, circuits are prepared for executing the control condition by closing front contacts 250 and 25L During the third on period the executing circuits are completed when relays F 'and'ZFP pick up. Since lever SGL in the control ofiice is shown in a position for putting signals to stop at the selected station, this particular condition will be executed in the as sumed example. More specifically, a circuit is closed which actuates polar contact 252 of the stop relay S to its right hand dotted position which circuit extends from (B+), front contact 265 of relay F front contact 263 of relay ZFP front contact 246 of relay S0 front contact 262 of relay lME back contact 266 of relay 3V front contact 250 of relay 2V and winding of relay S, to (ON). Although the detailed circuits have not been shown, it will be understood that the actuation of contact 252 to the right completes suitable circuits for putting the signals to stop.

During the third off period relay F is dropped so that the above mentioned executing circuit to relay S is deenergized. From the above example it will be seen how a particular control code is transmitted. It is not believed necessary to described in detail the transmission and reception of other control codes although it will be briefly explained how the two additional code combinations which are possible for a single step may be used for clearing signals east and for clearing signals west.

If, for example, relay 2ME remains picked up throughout the third on period (due to relay 20s in the control oflice being energized by lever 'SGL in its right hand dotted position), then a circuit is closed for energizing relay DR which extends from (B+), front contact 265 of relay F front contact 263 of relay 2FP front contact 246 of relay S0 front contact 241 of relay 2ME back contact 256 of relay 3V front contact 25! of relay 2V and winding of relay DR, to (ON). Relay DR actuates its polar contact 259 to the right. A circuit is also closed for actuating contact 252 of relay S to the left extending from (B-) front contact 25! of relay F front contact 256 of relay 2FP front contact 253 of relay S0 backicontact 262 of relay IME back contact 266 of relay 3V front Contact 250 of relay 2V and winding of relay S, to (CN). This energizes conductor 219 for clearing eastbound signals.

On the other hand, if relays IME and 2ME are not picked up during the third on period (because relays ICS and 208 in the control ofiice are deenergized by lever SGL in its left'hand dotted position) then relays S and DR will be positioned to the left because (B) is applied to both these relays through back contacts 262 and 241 of relays IME and ZME respectively. This obviously clears westbound signals by energizing conductor 26!).

End of operating cycZe. The operation of the system during a cycle has been explained in detail and it will now be pointed out how the system is returned to normal. As previously mentioned, the stepping relay bank in the control office takes one step for each off period. Thus, the picking up of relay 3V during the third on period causes the fourth energization of the stepping line with impulses. This in turn causes relay VP to drop for causing the fourth deenergization of the stepping line. This fourth deenergized or off period does not result in again picking up relays E and EP because with relay VP down and relay 3V up there is no circuit for energizing either winding of relay E. This produces a prolonged off period which allows relay SA in the control ofiice to drop its contacts. The dropping of frontcontact 28 of relay SA deenergizes all of the stepping relays and prevents the picking up of relay E. The closing of back contact I 5 of. relay SA permits the starting relay ST to be conditioned in readiness for the initiation of another cycle. The picking up of relay 3V prior to the dropping of relay SA causes relay CD to be deenergized by means of a circuit which is not shown but which may be the same as disclosed, for example, in the prior application ofv N. 1). Preston et al., Ser.

No. 455,304 filed May 24, 1930.

At the field station, the system is similarly restored to normal by the prolonged off period dropping the stepping relays when relay SA drops its front contact 222. The deenergization of the stepping relays opens the holding stick circuit of. relay S0 by reason of open front contact 245 of relay 2V The system is now in condition for the initiation of another cycle either from the control of-- fic-e or from a field station.

Indications-As previously mentioned, indications may be ready for transmission at a field station at the same time that controls are ready for transmission from the control oilice. The system is so arranged that simultaneous two-way or duplex transmission of controls and indications may occur during each cycle of operations. However, for convenience, the transmission or controls has been considered separately and the transmission of indications Will also be considered separately with the duplex operation considered under a separate heading.

It also may happen that there are several field stations which may have indications ready for transmission at the same time and they are reglstered in the control office one at a time in an order determined by the relative characteristics of their code calls. This feature of determining the order of station registration by the superiority of code plan will also be considered under a separate heading. The transmission of indications from the single typical station illustrated in Figs. 3 and 3a will be considered at this time.

Automatic Martina-A change in the position of a controlled device or the automatic change of a traific indicating device, such as the usual track relay, causes the system to be initiated by the energization of change storing relay CHS As soon as relay CHS is picked up, a pick-up circuit is closed for starting relay ST which extends from back contact 222 of relay SA front contact 261 of. relay CHS and winding of relay ST to Relay ST thus being picked up causes the normally energized B branch of the stepping line circuit to be opened at back contact 205 so that all of the IME relays are deenergized. The dropping of relay IME in the control ofiice closes a pick-up circuit for starting relay ST extending from back contact I6 of relay SA, back contact 58 of relay IME and winding of relay ST, to

The response of front contact I 8 of relay ST causes the system to be initiated and a series of impulses is applied to the stepping line circuit as previously described for marking oif the stepping operations of. the cycle. During this cycle, it will be assumed that no controls are being transmitted, therefore, none of the code sending relays ICS, 208 and 3CS in the control oflice are picked up so that during the on periods the stepping line circuit is not energized with impulses and the message line circuit is not energized with or impulses.

Such a code of no impulses applied to the stepping line and no or impulses applied to themessage line during the on periods of the cycle results in dropping out all of the SO relays at the field stations. This is because no field station has such a code combination assigned to it, since this code combination corresponds to the phantom code. This occurs irrespective of the fact that all the SO relays are picked up at the beginning of the cycle in the usual manner. The step-by-step operations ocour in the manner previously described so that a description of this portion of the cycle need not be repeated. A description of the registration of the particular transmitting station will now be given.

Station registration-The application of the first impulses to the stepping line circuit is repeated by the F relays at the control oflice and at the field stations. The closure of the front contacts of the line relay at the station which has initiated the system (assumed to be the station illustrated) causes relay S1 to be picked up over a circuit extending from front contact 22'! of relay F back contact 268 of relay SA front contact 269 of relay CHS and lower winding of relay SI to A holding stick circuit is closed for relay S1 extending from front contact 264 of, relay SA front contact 230 of relay F front contact 2' and lower winding of relay S1 to l The picking up of relay F is repeated by the sequential energizations of relays PP and 2FP The closure of front contact 229 of relay 2FP bridges front contact 230 of relay F so that the closure of. front contact 230 of relay F initially closes the holdingstick circuit for relay S1 while the front contact 229 of relay 2FP finally opens this holding stick circuit at each step. This operation is analogous to the operation of relay S0 except that the holding stick circuit for relay SO is closed during deenergized periods of the line while the holding stick circuit for relay SI is closed during the energized periods of the line.

After the predetermined time measuredofi by the picking up of relay SA the pick-up circuit of relay S1 is opened at back contact 268 of relay SA but since this contact is of the follow-up type the holding circuit through front contact 264 is closed before the pick-up circuit is opened.

It will now be assumed that relay S1 is maintained energized by reason of the fact that the code call impressed upon the line circuits during the off periods corresponds to the code call of the illustrated station, since it is assumed that this is the only station which is transmitting. As soon as the impulses are removed from the stepping line circuit, relay F drops its contact 230 and shortly thereafter relay 2FP drops its contact 229 for deenergizing the holding stick circult of relay S1 Before contact 229 is dropped, however, the selecting stick circuit of relay S1 is completed. Since jumper 206 is connected to bus 239 for picking up relay 2CS the message line circuit is energized with impulses during the first off period for picking up relays 2ME and 2ME. This circuit extends from the upper terminal of transformer TR, conductor I2, conductor 290, front contact 212 of relay 2CS winding of relay 2ME rectifier 2RA conductor 8, back contact II of relay F, winding of relay 2ME and rectifier RA to the lower terminal of transformer TR.

Since buses 238 and240 are deenergized at this time, relays ICS and 303 are down so that the stepping line circuit is not energized with impulses and the message line circuit is not energized with impulses. This is becauses during the off period front contacts 224 and 214 of relay F are dropped and'front contacts 225 and 215 of relays ICS and 3CS respectively are dropped. Of course, back contacts 204, 203 and 226 of relay S1 are open at this time. Front contact 213 of relay F is also open but this contact-is bridged by front contact 212 of relay 20S to energize the 2ME relays as above described.

The selecting stick circuit for relay S1 is now completed from back contact 23I of relay ICS back contact 232 of relay IME front contact 233 of relay 2CS front contact 234 of relay ZME back contact 235 of relay 3CS back contact 236 of relay 3ME front contact 216 and upper winding of relay S1 to When relay F picks up at the beginning of the second on period, the holding stick circuit for relay SI is closed at front contact 236 so that relay S1 is maintained energized during the on period. Relay IV is picked up during the second on period and its contact 243 switches from jumper 266 to 2! for energizing bus 238 and picking up relay ICS When relays F and 2FP drop their contacts 236 and 229 during the second off period, the selecting stick circuit for relay S1 is maintained energized from front contact 23I of relay ICS front contact 232 of relay IME back contact 233 of relay 2CS back contact 234 of relay 2ME back contact 235 of relay 3CS back contact 236 of relay 3ME front contact 216 and upper winding of relay S1 to It will be understood that relay IME is picked (and relay IME in the oifice is picked up) because relay ICS has its front contact 225 closed for energizing the stepping line circuit with impulses during the second off period.

Relays F and 2FP are picked up during the third on period and relay 2V picks up to close the permanent stick circuit for relay S1 This permanent stick circuit is effective to maintain relay SI energized until the end of the cycle and extends from front contact 211 of relay 2V front contact 21! and lower winding of relay SI to Referring to the control ofiice circuits, it will be recalled that relay 2ME was picked up during the first off period and relay IME was picked up during the second off period, in series with corresponding relays at the transmitting field station. During the first and second off periods this code combination is registered in the control office on suitable pilot relays which for convenience have not been illustrated but which may be of any suitable type, such as disclosed in the pending application of N. D. Preston et al., Ser. No. 455,304 filed May 24, 1930. It is sufficient for an understanding of the present invention to know that the conditions of the ME relays in the control office are executed during each off period to condition a suitable pilot relay when the F and ZFP relays are deenergized.

During each executing period a circuit is closed either from (3+) or (B) through back contacts 60 or 62 of relay F, 6I or 63 of relay 2FP, to front and back contacts of the three ME relays.

- These circuits are then extended by way of' the front and back contacts of the ME relays in the positions to which they have been actuated by the code call from the transmitting station, through selecting contacts 64 to 69 inclusive of the stepping relays to the conductors leading to bracket 13 and thence to the particular pilot relays, all of which will be readily understood.

For example, during the first off period with relay 2ME picked up and relays IME and 3ME down, a first executing circuit is completed which extends from (B-|-), back contact 66 of relay F, back contact 6| of relay ZFP, front contact 14 of relay 2ME, back contact H of relay 3V, back contact 61 of relay 2V and front contact 66 of relay IV, to conductor 59. Since relay IME is down at this time, a second executing circuit is completed which extends from (B'-), back contact 62 of relay F, back contact 63 of relay 2FP, back contact 15 of relay IME, back contact III of relay 3V, back contact of relay 2V and front contact 64 of relay IV, to conductor 16. Since relay 3ME is down at this time, a third executing circuit extends from (B) through back contacts 62 and 63 of relays F and 2FP and thence through back contact 11 of relay "3ME, back contact 12 of relay 3V, back contact 69 of relay 2V and front contact 68 of relay IV, to conductor 18.

During the second off period, with relay IME picked up and relays 2ME and 3ME dropped, it will be obvious how (B+) is extended by way of front contact 65 of relay 2V to conductor 19 and (B) is extended by way of front contacts Gland 69 of relay 2V to conductors 86 and 8|.

Following the registration of the code call impressed upon the line circuits, the station relay C is picked up through the contact selection of the pilot relays. Relay C corresponds to the particular station illustrated in Fig. 3 and this relay connects the indication storing relays. such as IIR and 21R. associated with this station, to buses which are sequentially energized in accordance with the indications received after the station is registered. 7

More specifically, the pilot relays are positioned on the first two steps in accordance with the polarities applied to the conductors leading to bracket 13. Buses I, 2 and 3 are energized in accordance with the indications received on the third step since these buses .are selected by front contacts 10, H and I2 of relay 3V. Assuming relay C energized, then upon the third off period indication buses l, 2 and 3 are energized with (3+) or (B) in accordance with the condition of the three message receiving relays.

With relay WP of Fig. 3 in the position illustrated for indicating the track switch in its normal locked position, for example when relay 2V is picked up during the third on period, a circuit is closed for energizing relay 2CS which extends from back contact 241 of relay 3V front contact 242 of relay 2V front contact 218 of relay W1 contact 219 of relay WP in its left hand position, bus 239 and winding of relay 208 to During the third off period, the dropping of front contacts 224, 213 and 214 of relay F attempts to deenergize the line circuits but since front contact 212 of relay 2CS is closed, the message line circuit is energized by way of the A branch, that is, with (-1-) impulses. This picks up relay ZME in the control ofiice and establishes a circuit for energizing relay 21R which extends from (3+) back contacts 69 and El of relays F and 2FP respectively, front contact 14 of relay ZME, front contact "ll of relay 3V, front contact 82 of relay C, and winding of relay ZIR, to (ON).

Relay ZIB; is positioned to the right and since the other ME relays are down (B) is connected to buses l and 3, Bus l is extended by Way of front contact 83 of relay C to the winding of relay [IR and this relay is positioned to the left. A circuit is now closed from through contact 84 of relay IIR in its left hand position and contact 85 of relay 21R in its right hand position to energize normal lamp N as an indication that the corresponding track switch at the field station is in its normal locked position.

On the other hand, if polar contact 219 of relay WP is in its right hand dotted position, then relays ICS 2CS and 3CS remain down when relay 2V takes its step. This results in relays IME, 2ME. and 3ME remaining down. A circuit is closed from (B). back contacts 62 and 63 of relays F and 2FP, back contact 1'! of relay 3ME and front contact "I2 of relay 3V to bus 3. This circuit is not shown complete since it may be used for additional indications. (B) is also applied to buses I and 2 because relays IME and ZME are down. This positions relays IIR and 21B to the left for lighting reverse lamp R.

In the event that relay WP is in its unlocked position, then relay ICS is picked up for energizing the stepping line with impulses which picks up relay IME in the control oflice. This extends (B+) by way of bus I to relay IIR for positioning this relay to the right. The (B) applied to bus -2 will of course position relay 21R to the left but neither lamp is energized with contact 84 in its right hand dotted position, which is an indication that the track switch is in its unlocked condition.

After the registration of a station and the transmission of its indications, the system returns to normal as previously described.

It is believed that the above example of registering the illustrated station in the control ofiice is sufficient to indicate how other stations having different combinations of code jumpers such as 200 and 201 are effective to register themselves by providing distinctive code calls for each station. It is obvious that the same code combinations are available for transmitting inbound codes during the off periods as are available for transmitting outbound codes during the on periods. It will be noted that the same combinations are obtainable with the code selecting relays at the field station as are obtained with the code selecting relays in the control oflice. Those combinations in the control office are made up during the on periods when relay F has its back contacts i5, l I and I3 picked up, while they are made up at the field station when relay F has its front contacts 224, 213 and 274 dropped. Thus, a choice of eight combinations for station registration is obtained for the first step, a choice of sixty-four is obtained for the second step and so on in the same manner as described in connection with controls.

It is also believed unnecessary to recite other examples relating to the transmission of indications from a registered station, since it is believed obvious how these indications are effective to position indication receiving relays during additional steps in the same manner as in the example cited for the third step of the cycle.

Pluralzty of stations transmitting.In accordance with this invention, only one station can register itself in the control oflice during an operating cycle regardless of the number of stations which may have their SI relays picked up at the beginning of the cycle. The sequence or order in which the stations communicate theirindications, one station at a time is determined by the characteristics of the code calls of these stations.

With reference to the second typical code table given above, which is applicable to both station selection and station registration, a and a symbol are assigned to represent the energized condition of the A and B branches of the message line and the B branch of the stepping line, while the"0 symbol is assigned to represent the open or deenergized .condition of these branches during the off periods. The code call for the first two steps in, this table is assigned to the illustrated station both for outbound and inbound transmission. Since the branches indicated in this table are in series circuits, they may be opened at any field station during the off periods by the code selecting relay front contacts irrespective of the closed condition of the corresponding contacts at any other field station.

In other words, the open condition represented by the 0 symbol is the most superior condition and any field station having such a code element in its code call is superior to all other stations having a or a symbol in its code call for the corresponding period of the cycle.

This feature may be more readily understood by consideration of the code call of the illustrated station. It will be noted from the second typical code table that the B branch of the stepping line and the B branch of the message line are opened while the A branch of the message line is energized with (-1-) impulses on the first step. This is due to relay 2CS being picked up. Since the polarity of the impulses which energize these two line circuits is of no consequence during this portion of the operation, it need only be considered that these three branches are energized or not energized as indicated.

Since code jumper 205 is not connected to bus 238, the B branch of the stepping line is deenergized (opened) during the first off period.

'I'hosestations with a code element for the 'B branch of the stepping line (see second column of first typical code table) are inferior and cannot impress their code elements upon this branch while the illustrated station is impressing its 0 code element upon this branch. The SI relays at those inferior stations will be dropped out because those stations can not energize their IME relays (with suitable exponents) to efiect correspondence between contacts such as 23! and 232 of relays such as iCS and IMF. The first code selecting relays such as ICS will'be picked up at those stations because jumpers similar to 200 will connect to buses similar to-238, but the first message relay such as IME. will not be picked up because this branch of the line circuits cannot be energized.

At the superior stations, the condition (deenergized) of the B branch of the stepping line corresponds to the condition of the buses such as 238 (deenergized) so that correspondence exists between the relays such as ICS and IME Since code jumper 200 is connected to bus 239, the A branch of the message line is energized (closed) during the first off period. Those stations with a code element for'the A branch of the message line (see third column of first typical code table) on this step are inferior (including the'illustratedstation) and cannot impress their code call elements upon this branch when a station is impressing its 0 code element upon this branch.

The SI relays at those inferior stations will be dropped out because they cannot energize their ZME relays (with suitable exponents) to effect correspondence between contacts such as 233 and 234 of relays such as -2CS and 2ME In the assumed example however, the illustrated station will not be dropped out if there is no other station transmitting with a 0 code element associated with the A branch of the stepping line.

Since code jumper 200 is not connected to bus 240, the B branch of the message line is de-energized (opened) during the first ofif period. These stations with a code element for the B branch of the message line (see fourth column of first typical code table) on this step are inferior and cannot impress their code call elements upon this branch while the illustrated station is impressing its 0 code element upon this branch.

The SI relays at those inferior stations will be dropped out because those stations cannot energize their 3ME relays (with suitable exponents) to effect correspondence between contacts such as 235 and 236 of relays such as 3CS and 3ME The third code selecting relays such as 308 will be picked up at those stations because jumpers similar to 200 will connect to buses similar to 240, but the third message relays will not be picked up because this branch of the line circuits cannot be energized.

At the superior stations, the condition (de-energized) of the B branch of the message line corresponds to the condition of the buses such as 240 (do-energized) so that correspondence exists between the relays such, as 3CS 'and 3ME Irrespective of the number of stations transmitting at the same time, the most superior station maintains its SI relay picked up and the SI relays at the other stations are dropped out in groups. In the present embodiment, since sta tion registration is accomplished with two steps, it is possible to register any one of 63 stations in the control oifice on 'two steps, that is, eight .times eight minus the phantom station. For the first step of the cycle, at one-eighth of the stations, jumpers similar to 209 will be connected as shown for the typical field station of Fig, 3. Therefore, assuming all stations transmitting, eight stations will maintain their SI relays picked up during the first step and the remaining stations will drop out their SI relays. During the second step, only one-eighth of the selected stations (one station) will have a jumper 20! connected as illustrated in Fig. 3 and this will be the station which will be finally selected during this step. The remaining seven stations will be dropped out on the second step.

It is believed unnecessary to explain in further detail the manner in which the stations are given preference over one another in accordance with their code characteristics as the feature of superiority of code has been explained in detail in the above mentioned application Ser. No. 455,304. It will be understood that the use of the superiority of code is adaptable to a system arranged in accordance with the present invention but the invention is not necessarily limited to such a system. It will also be understood that each of the sixty-three possible stations which may be registered during two steps in the present embodiment will have code jumpers corresponding to 260 and 20! connected in sixty-three difierent combinations, one combination for each station. Of course, some of these stations will have more than one jumper corresponding to 200 connected to more than one bus corresponding to 238, 239 and 240. Likewise, there will be one, two and three jumpers similar to 2M at the stations connecting to buses 238, 239 and 240 in all possible combinations.

Duplex transmission-From the above description it is apparent that the stepping and message line circuits are employed for the transmission of controls during the on periods of the cycle, as marked off by the energization of the stepping line with impulses, while indications are transmitted over the stepping and message line circuits during the off periods of the cycle, as marked off by the disconnection of the impulses from the stepping line circuit.

This is accomplished in accordance with the present invention by providing the line relays at the various stations with front contacts which shunt'the front contacts of the code sending relays during the on periods and remove the shunts from the code sending relay contacts during the off periods. The line relay in the con- 'trol ofiice is provided with back contacts which shunt the front contacts of the code sending re- "lays during the off periods and remove these shunts during the on periods. In other words, the on and off conditions of the A branch of the stepping line circuit for each step are employed successively for the transmission of controls and indications for that step. Thus it is .trols alone, a code callis applied to the stepping 

